Laubach said both entities are currently performing tests, but that the gas readings were so faint that most of their equipment did not pick up any gas at all.

"They're trying to isolate it right now," Laubach said. "You could smell the gas, but it was very minimal. Most of our detectors didn't get any readings."

Students were evacuated from the 851 North 15th Street building, but were allowed back into the school at 2:35 p.m. to pick up their personal belongings, Benner said. They will then be sent home, and there will be no after-school activities.

The Trexler Middle School will be open for school Tuesday.

Parents and guardians were notified about the evacuation via the school district's messenger system, Benner said.